Beginner Python common exception error, there is always one you encounter!

Beginner Python common errors

Colon forget to write
Misuse =
Error tightening
Variable is not defined
Errors in text input
Different types of data splicing
Index location problem
Use the key does not exist in the dictionary
Forget the brackets
Leakage pass parameters
Missing dependencies
Use of keywords in python
Coding problems

1. forget to write a colon

Forget to add in the back if, elif, else, for, while, def statement :

age = 42

if age == 42

    print('Hello!')
  File "<ipython-input-19-4303141d6f97>", line 2

    if age == 42

                ^

SyntaxError: invalid syntax

2. Misuse `=`

'''
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'''
=` 是赋值操作，而判断两个值是否相等是 `==
gender = '男'

if gender = '男':

    print('Man')
  File "<ipython-input-20-191d01f95984>", line 2

    if gender = '男':

              ^

SyntaxError: invalid syntax

3. Error indentation

Python distinguish between code block, common errors with usage indent:

print('Hello!')

 print('Howdy!')
  File "<ipython-input-9-784bdb6e1df5>", line 2

    print('Howdy!')

    ^

IndentationError: unexpected indent
num = 25

if num == 25:

print('Hello!')
  File "<ipython-input-21-8e4debcdf119>", line 3

    print('Hello!')

        ^

IndentationError: expected an indented block

4. The variable is not defined

'''
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'''
if city in ['New York', 'Bei Jing', 'Tokyo']:

    print('This is a mega city')
---------------------------------------------------------------------------

NameError                                 Traceback (most recent call last)

<ipython-input-22-a81fd2e7a0fd> in <module>

----> 1 if city in ['New York', 'Bei Jing', 'Tokyo']:

      2     print('This is a mega city')
NameError: name 'city' is not defined

5. errors in text input

Colon
English brackets
Comma
English single and double quotation marks

if 5>3：

    print('5比3大')
  File "<ipython-input-46-47f8b985b82d>", line 1

    if 5>3：

          ^

SyntaxError: invalid character in identifier
if 5>3:

    print('5比3大'）
  File "<ipython-input-47-4b1df4694a8d>", line 2

    print('5比3大'）

                ^

SyntaxError: invalid character in identifier
spam = [1, 2，3]
  File "<ipython-input-45-47a5de07f212>", line 1

    spam = [1, 2，3]

                 ^

SyntaxError: invalid character in identifier
if 5>3:

    print('5比3大‘)
  File "<ipython-input-48-ae599f12badb>", line 2

    print('5比3大‘)

                 ^

SyntaxError: EOL while scanning string literal

6. The different data types splicing

String / list / tuple support splicing

Dictionary / collection does not support splicing

'''
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'''
'I have ' + 12 + ' eggs.'

#'I have {} eggs.'.format(12)
---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-29-20c7c89a2ec6> in <module>

----> 1 'I have ' + 12 + ' eggs.'
TypeError: can only concatenate str (not "int") to str
['a', 'b', 'c']+'def'
---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-31-0e8919333d6b> in <module>

----> 1 ['a', 'b', 'c']+'def'
TypeError: can only concatenate list (not "str") to list
('a', 'b', 'c')+['a', 'b', 'c']
---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-33-90742621216d> in <module>

----> 1 ('a', 'b', 'c')+['a', 'b', 'c']
TypeError: can only concatenate tuple (not "list") to tuple
set(['a', 'b', 'c'])+set(['d', 'e'])
---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-35-ddf5fb1e6c8c> in <module>

----> 1 set(['a', 'b', 'c'])+set(['d', 'e'])
TypeError: unsupported operand type(s) for +: 'set' and 'set'
grades1 = {'Mary':99, 'Henry':77}

grades2 = {'David':88, 'Unique':89}

grades1+grades2
---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-36-1b1456844331> in <module>

      2 grades2 = {'David':88, 'Unique':89}

      3 

----> 4 grades1+grades2
TypeError: unsupported operand type(s) for +: 'dict' and 'dict'

7. The index location of the problem

spam = ['cat', 'dog', 'mouse']

print(spam[5])
---------------------------------------------------------------------------

IndexError                                Traceback (most recent call last)

<ipython-input-38-e0a79346266d> in <module>

      1 spam = ['cat', 'dog', 'mouse']

----> 2 print(spam[5])
IndexError: list index out of range

8. key does not exist in the dictionary

Access key in the dictionary objects can be used [],

But if the key does not exist, it will lead to: KeyError: 'zebra'

'''
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'''
spam = {'cat': 'Zophie',

        'dog': 'Basil',

        'mouse': 'Whiskers'}

print(spam['zebra'])
---------------------------------------------------------------------------

KeyError                                  Traceback (most recent call last)

<ipython-input-39-92c9b44ff034> in <module>

      3         'mouse': 'Whiskers'}

      4 

----> 5 print(spam['zebra'])
KeyError: 'zebra'

To avoid this, a method can use the get

spam = {'cat': 'Zophie',

        'dog': 'Basil',

        'mouse': 'Whiskers'}

print(spam.get('zebra'))
None

When the key does not exist, get the default return None

9. forget the brackets

When the function is passed in function or method, it is easy to write leak brackets

'''
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'''
spam = {'cat': 'Zophie',

        'dog': 'Basil',

        'mouse': 'Whiskers'}

print(spam.get('zebra')
  File "<ipython-input-43-100a51a7b630>", line 5

    print(spam.get('zebra')

                           ^

SyntaxError: unexpected EOF while parsing

10. The drain-parameters

def diyadd(x, y, z):

    return x+y+z

diyadd(1, 2)
---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-44-7184f3f906ca> in <module>

      2     return x+y+z

      3 

----> 4 diyadd(1, 2)
TypeError: diyadd() missing 1 required positional argument: 'z'

11. The lack of dependent libraries

No computer library

12. Use of the Image python

如try、except、def、class、object、None、True、False等

'''
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'''
try = 5

print(try)
  File "<ipython-input-1-508e87fe2ff3>", line 1

    try = 5

        ^

SyntaxError: invalid syntax
def = 6

print(6)
  File "<ipython-input-2-d04205303265>", line 1

    def = 6

        ^

SyntaxError: invalid syntax

13. The file encoding problem

import pandas as pd

df = pd.read_csv('data/twitter情感分析数据集.csv')

df.head()

Try encoding encoding parameters passed in utf-8, gbk

df = pd.read_csv('data/twitter情感分析数据集.csv', encoding='utf-8')

df.head()

Are being given instructions and encoding is not utf-8 gbk, but are not common coding, where we need to pass both the right encoding, in order to let the program run.

There chardet python library, designed to detect coding.

import chardet

binary_data = open('data/twitter情感分析数据集.csv', 'rb').read()

chardet.detect(binary_data)
{'encoding': 'Windows-1252', 'confidence': 0.7291192008535122, 'language': ''